1. Field of the invention
The present invention relates to a display device for providing a large picture image screen by arranging regularly a large member of display panels. More particularly, it relates to such a display device in which correction can be made for each display panel.
2. Description of the prior art
FIG. 7 is a cross-sectional view showing a part of a picture image screen of a conventional display device which comprises a plurality of display units 1 regularly arranged in the vertical and horizontal directions in a plane to constitute a large picture image screen, each of the display units holding a plurality of multi-color display panels such as liquid crystal panels each of which consists picture elements: red, blue and green.
Each pair of adjustable volumes 3 provided in each of the display units 1 are connected to a control panel (not shown) placed at the reverse side of the display units so that by operating a knob of each of the adjustable volumes, a driving signal for the display panel is controlled through a driving circuit provided in the control panel, whereby the total brightness of the display panel 2 balance in the three colors, i.e. red, blue and green can be adjusted.
In the conventional display device having the construction as above-mentioned, adjusting of the picture screen has been carried out as follows.
Firstly, adjustment is carried out for each display unit 1 having a plurality of the display panels 2. The display panels 2 are operated while the total brightness and balance in colors (color tone) of each picture element of red, blue and green are adjusted in comparison with standard values. In the next place, a plurality of the display units 1 adjusted are attached to the frame (not shown) of the display device in the vertical and transverse directions in a plane to form a large picture image screen by a number of the display panels. Adjustment of a picture displayed on the large screen is carried out as follows. The display panels 2 are operated to display a picture on the large image screen and the total brightness and balance of colors: red, blue and green are observed. Since there is difference in the characteristics of each of the display panels 2, it is necessary to readjust the display panels as a whole to give the optimum condition by operating the adjustable volumes 3 provided in the control panel (not shown) at the reverse side of each of the display units 1.
In the conventional device, the adjustable volumes 3 are provided only to the display unit as an element constituting a picture screen. It is, therefore, easy that the single display unit 1 is adjusted by the adjustable volumes. However, when a number of display units 1 are arranged on the frame of the display device to form a large picture screen, there is scattering in the characteristics of the display units 1, whereby there is unevenness in brightness and color tone in the total picture image. In this case, readjustment is needed by operating the adjustable volumes 3 provided at the reverse side of each of the display units 1. In the readjustment, an operator has to stand in front of the picture screen to specify any part requiring adjustment. Then, the operator goes to the reverse side of the picture screen to operate the adjustable volumes 3, and he returns to the front of the screen to confirm whether or not the readjustment is made correctly. Thus, the readjustment operation is manually made and it is troublesome.
The display device is sometimes installed at a relatively small area. In this case, a space for working is limited, and it is difficult to manually operate the adjustable volumes 3.